Lens barrel and imaging device

ABSTRACT

The lens barrel includes a first lens unit, a second lens unit, and a drive unit. The first lens unit includes a first lens element and a first lens support frame supporting the first lens element. The second lens unit includes a second lens element and a second lens support frame supporting the second lens element. The second lens unit is supported by the first lens unit to be movable in the optical axis direction of the first lens element with respect to the first lens unit. The drive unit is arranged to be used to drive the second lens unit with respect to the first lens unit, and is fixed to the first lens unit. When viewed in the optical axis direction, the drive unit is fixed to the first lens unit so that a first profile line formed by the first lens unit and the drive unit is substantially circular.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Japanese Patent Application No.2008-230163 filed on Sep. 8, 2008. The entire disclosure of JapanesePatent Application No. 2008-230163 is hereby incorporated herein byreference.

BACKGROUND

1. Technical Field

The technical field relates to a lens barrel with which the focal lengthcan be changed.

2. Description of the Related Art

Conventional digital cameras make use of a zoom lens system with whichthe focal length can be varied while the object distance of a subjectthat is in focus (hereinafter also referred to as the subject distance)is kept substantially constant. For example, zoom lens systems areemployed in compact digital cameras and digital cameras withinterchangeable lenses.

With a conventional lens barrel, for example, as the zoom mechanismoperates, the focus lens unit including the focus lens is moved in theoptical axis direction by a cam mechanism. This allows the focal lengthto be varied while the subject distance is kept substantially constant(see, for example, Japanese Laid-Open Patent Application 2006-113289).

A phase difference detection system has been employed as the auto-focussystem with conventional interchangeable lens digital cameras.

More recently, however, an interchangeable lens digital camera has beenproposed that makes use of a contrast detection system forauto-focusing. With this contrast detection system, for example, thefocus lens unit is moved in the optical axis direction while evaluationvalues at various positions of the focus lens unit are found on thebasis of image data. The focus lens unit is moved until the evaluationvalue goes past its peak, after which the evaluation value is returnedto its maximum position to focus the subject image (an optical image ofthe subject). Thus, in auto-focusing by contrast detection, it isnecessary to move the focus lens unit back and forth in the optical axisdirection.

Also, since the focus needs to be continued during the capture of movingpictures, the focus lens unit has to be continuously moved back andforth and the peak of the evaluation value detected.

Thus, when a contrast detection system is used, since the focus lensunit is moved in the optical axis direction, making the focus lens unitsmaller is preferable when drive speed is taken into account.

SUMMARY

However, if a configuration is employed in which the focus lens unit isdriven in the optical axis direction by a cam mechanism, as with thelens barrel described in Japanese Laid-Open Patent Application2006-113289, the size of the focus lens unit becomes larger, or theweight of the focus lens unit increases.

In view of this, the inventors of the present invention studied a lensbarrel with which drive of the zoom mechanism is performed only bymanual operation by the user, and drive of the focus lens unit withrespect to the zoom mechanism is performed only by actuator. In thiscase, the structure of the focus lens unit and its surrounding parts issimplified, so the focus lens unit can be made more compact.

However, if a motor is used as the actuator that drives the focus lens,when the motor is attached to the lens barrel, the motor sticks outconsiderably to the outside of the lens barrel, and this hampers theeffort to make the lens barrel more compact.

The lens barrel according to a first aspect comprises a first lens unit,a second lens unit, and a drive unit. The first lens unit includes afirst lens element and a first lens support frame supporting the firstlens element. The second lens unit includes a second lens element and asecond lens support frame supporting the second lens element. The secondlens unit is supported by the first lens unit to be movable in theoptical axis direction of the first lens element with respect to thefirst lens unit. The drive unit is arranged to be used to drive thesecond lens unit with respect to the first lens unit, and is fixed tothe first lens unit. When viewed in the optical axis direction, thedrive unit is fixed to the first lens unit so that a first profile lineformed by the first lens unit and the drive unit is substantiallycircular.

With this lens barrel, when viewed in the optical axis direction, thedrive unit is fixed to the first lens unit so that a first profile lineformed by the first lens unit and the drive unit is substantiallycircular, so the drive unit does not stick as far outside from the firstlens unit. This allows the lens barrel to be more compact. Also, areduction in size is possible with an imaging device equipped with thislens barrel.

The phrase “a first profile line is substantially circular” hereincludes not only a case in which the first profile line formed by thefirst lens unit and the drive unit is completely circular, but also acase in which the first profile line deviates from being circular to theextent that the lens barrel size can still be reduced.

In determining whether or not the first profile line is substantiallycircular, even if a portion that sticks out to the outside, such as acam pin, is provided to the first lens unit, the shape of that portionis not taken into account.

The lens barrel according to a second aspect comprises a first lensunit, a second lens unit, and a drive unit. The first lens unit includesa first lens element and a first lens support frame supporting the firstlens element. The second lens unit includes a second lens element and asecond lens support frame supporting the second lens element. The secondlens unit is supported by the first lens unit to be movable in theoptical axis direction of the first lens element with respect to thefirst lens unit. The drive unit is arranged to be used to drive thesecond lens unit with respect to the first lens unit, and is fixed tothe first lens unit. The second lens unit includes a transmission membersupported rotatably around a second rotational axis by the second lenssupport frame and arranged to convert the rotary motion of the driveshaft into linear motion in the optical axis direction, and an elasticmember imparting rotational force around the second rotational axis tothe transmission member so that the transmission member moves to theouter peripheral side with respect to the second lens support frame. Thetransmission member includes a transmission member body having anapproximate U shape that opens on the opposite side from the secondrotational axis, and arranged to transmit drive force from the driveunit. The transmission member body opens toward the approximatecircumferential direction in a state in which the drive unit is fixed tothe first lens unit.

The lens barrel here also encompasses an interchangeable lens unit thatis used in an interchangeable lens type of imaging device, in additionto a lens barrel that is integrated with a camera body. The imagingdevice also encompasses an interchangeable lens type of imaging device,in addition to an imaging device in which the camera body and the lensbarrel are integrated. Examples of possible imaging devices includedigital still cameras, interchangeable lens digital cameras, digitalvideo cameras, portable telephones with a camera function, and PDAs(Personal Digital Assistants) with a camera function. The imaging deviceencompasses devices capable of capturing only still pictures, devicescapable of capturing only moving pictures, and devices capable ofcapturing still pictures and moving pictures.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the attached drawings which form a part of thisoriginal disclosure:

FIG. 1 is a simplified diagram of a digital camera;

FIG. 2 is a block diagram of the configuration of a camera body;

FIG. 3 is a simplified oblique view of a digital camera;

FIG. 4A is a top view of a camera body, and FIG. 4B is a rear view of acamera body;

FIG. 5 is a cross section of an interchangeable lens unit (wide angleend);

FIG. 6 is a cross section of an interchangeable lens unit (wide angleend);

FIG. 7 is a cross section of an interchangeable lens unit (telephotoend);

FIG. 8 is a cross section of an interchangeable lens unit (telephotoend);

FIG. 9 is an exploded oblique view of a second lens group unit and afocus lens unit;

FIG. 10 is an exploded oblique view of a second lens group unit and afocus lens unit;

FIG. 11 is an oblique view of the focus lens unit;

FIG. 12 is an oblique view of the focus lens unit;

FIG. 13A is a diagram of the configuration of the optical system at thewide angle end, and FIG. 13B is a diagram of the configuration of theoptical system at the telephoto end;

FIG. 14 is a graph of the relationship between the rotational angle ofthe zoom ring and the distance of the various members from the imagingsensor;

FIG. 15 is a tracking table used for a zoom lens system;

FIG. 16 is a plan view of the focus lens unit;

FIG. 17 is a plan view of the focus lens unit (during assembly); and

FIG. 18 is a plan view of the focus lens unit (another embodiment).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Selected embodiments will now be explained with reference to thedrawings. It will be apparent to those skilled in the art from thisdisclosure that the following descriptions of the embodiments areprovided for illustration only and not for the purpose of limiting theinvention as defined by the appended claims and their equivalents.

First Embodiment

Summary of Digital Camera

A digital camera 1 will be described through reference to FIGS. 1 to 14.FIG. 1 is a simplified diagram of the digital camera 1. As shown in FIG.1, the digital camera 1 (an example of the imaging device) is a digitalcamera with an interchangeable lens, and mainly comprises a camera body3 and an interchangeable lens unit 2 (an example of the lens barrel)that is removably mounted to the camera body 3. The interchangeable lensunit 2 is mounted via a lens mount 95 to a body mount 4 provided to thefront face of the camera body 3.

FIG. 2 is a block diagram of the configuration of the camera body 3.FIG. 3 is a simplified oblique view of the digital camera 1. FIG. 4A isa top view of the camera body 3, and FIG. 4B is a rear view of thecamera body 3. FIGS. 5 to 8 are simplified cross sections of theinterchangeable lens unit 2. FIGS. 5 and 6 show the state at the wideangle end, and FIGS. 7 and 8 show the state at the telephoto end. FIG. 6is a cross section in a different plane from that of FIG. 5. FIG. 8 is across section in a different plane from that of FIG. 7. FIGS. 9 and 10are exploded oblique views of a second lens group unit 77 and a focuslens unit 75. FIGS. 11 and 12 are oblique views of the focus lens unit.FIGS. 13A and 13B are diagrams of the configuration of an optical systemL. FIG. 13A shows the state at the wide angle end, and FIG. 13B showsthe state at the telephoto end. FIG. 14 is a graph of the relationshipbetween the rotational position of a zoom ring 84 and the distance ofthe various members from an imaging sensor 11.

In this embodiment, a three-dimensionally perpendicular coordinatesystem is set with respect to the digital camera 1. The optical axis AZof the optical system L (discussed below) coincides with the Z axisdirection (an example of the optical axis direction). The X axisdirection coincides with the horizontal direction when the digitalcamera 1 is in its portrait orientation, and the Y axis directioncoincides with the vertical direction when the digital camera 1 is inits landscape orientation. In the following description, “front” meanson the subject side of the digital camera 1 (the Z axis positivedirection side), and “rear” means the opposite side from the subjectside of the digital camera 1 (the user side, or the Z axis directionnegative side).

Interchangeable Lens Unit

The basic configuration of the interchangeable lens unit 2 will bedescribed through reference to FIGS. 1 to 14. As shown in FIG. 1, theinterchangeable lens unit 2 has the optical system L, a lens supportmechanism 71 that supports the optical system L, a focus adjusting unit72, an aperture adjusting unit 73, a blur correction unit 74, and a lensmicrocomputer 40 (an example of the drive controller).

(1) Optical System

The optical system L is a zoom lens system for forming an optical imageof a subject, and is mainly made up of four lens groups. Morespecifically, as shown in FIGS. 13A and 13B, the optical system L has afirst lens group G1 having a positive refractive power, a second lensgroup G2 having a negative refractive power, a third lens group G3having a negative refractive power, and a fourth lens group G4 having apositive refractive power.

The first lens group G1 has a first lens L1 and a second lens L2disposed on the imaging sensor 11 side of the first lens L1. The firstlens L1 is a negative meniscus lens having a convex face that faces thesubject side. The second lens L2 is a positive meniscus lens having aconvex face that faces the subject side, and is joined to the first lensL1 via an adhesive layer.

The second lens group G2 has a third lens L3, a fourth lens L4 disposedon the imaging sensor 11 side of the third lens L3, and a fifth lens L5(an example of the first lens element) disposed on the imaging sensor 11side of the fourth lens L4. The third lens L3 is a negative meniscuslens having a convex face that faces the subject side. The fourth lensL4 is a biconcave lens. The fifth lens L5 is a biconvex lens.

The third lens group G3 is made up of a sixth lens L6 (an example of thesecond lens element). The sixth lens L6 is a negative meniscus lenshaving a convex face that faces the imaging sensor 11 side, and isdisposed in the Z axis direction between the fifth lens L5 and a seventhlens L7 (in the Z axis direction between the second lens group G2 andthe fourth lens group G4).

The fourth lens group G4 has the seventh lens L7 (an example of thesecond lens element), an eighth lens L8, a ninth lens L9, a tenth lensL10, an eleventh lens L11, and a twelfth lens L12. The seventh lens L7is a positive meniscus lens for blur correction, and has a convex facethat faces the imaging sensor 11 side. The eighth lens L8 is a biconvexlens. The ninth lens L9 is a biconcave lens, and is joined to the eighthlens L8 via an adhesive layer. The tenth lens L10 is a biconvex lens.The face of the tenth lens L10 on the subject side is aspherical. Theeleventh lens L11 is a negative meniscus lens having a convex face thatfaces the subject side, and is joined to the tenth lens L10 via anadhesive layer. The twelfth lens L12 is a biconvex lens.

As shown in FIGS. 13A, 13B, and 14, when zooming in from the wide angleend to the telephoto end, the first lens group G1 to fourth lens groupG4 each move in the Z axis direction along the optical axis AZ towardthe subject side. More precisely, when zooming in from the wide angleend to the telephoto end, the space between the first lens group G1 andthe second lens group G2 increases, the space between the second lensgroup G2 and the third lens group G3 increases, and the space betweenthe third lens group G3 and the fourth lens group G4 decreases. Anaperture unit 62 (discussed below) moves to the subject side along withthe fourth lens group G4.

When focusing from an infinity focal state to a close focal state, thethird lens group G3 moves along the optical axis AZ to the subject side.

Furthermore, the seventh lens L7 moves in two directions perpendicularto the optical axis AZ in order to suppress blurring in the opticalimage attributable to movement of the digital camera 1.

(2) Lens Support Mechanism

The lens support mechanism 71 is for movably supporting the opticalsystem L, and has the lens mount 95, a fixed frame 50, a cam barrel 51,a first holder 52, a first lens group support frame 53, a second lensgroup support frame 54 (an example of the support frame), a secondholder 55 (an example of the first lens support frame), a third lensgroup support frame 56 (an example of the second lens support frame), afourth lens group support frame 61, a zoom ring unit 83 (an example ofthe zoom mechanism), and a focus ring unit 88.

The lens mount 95 is the portion of the camera body 3 that is mounted tothe body mount 4, and has a lens-side contact 91. The fixed frame 50 isa member that rotatably supports the cam barrel 51, and is fixed to thelens mount 95. The fixed frame 50 has a protrusion 50 a at the end onthe Z axis direction positive side, three concave portions 50 b providedto the outer periphery, and three linear through-grooves 50 c disposedat an equal pitch around the optical axis AZ. The cam barrel 51 hasthree convex portions 51 a provided to the inner periphery, three firstcam grooves 51 d, three second cam grooves 51 b, and three third camgrooves 51 c. Since the convex portions 51 a of the cam barrel 51 areinserted into the concave portions 50 b of the fixed frame 50, in astate in which relative movement is restricted in the Z axis direction,the cam barrel 51 is supported by the fixed frame 50 to be rotatablewith respect to the fixed frame 50.

The first lens group support frame 53 is fixed to the first holder 52and supports the first lens group G1. The first holder 52 has alongitudinal groove 52 a that is formed on the inner peripheral side andextends in the Z axis direction, and three cam pins 81 that are disposedat a constant pitch around the optical axis AZ. The protrusion 50 a ofthe fixed frame 50 is inserted in the longitudinal groove 52 a. The campins 81 are inserted in the first cam grooves 51 d of the cam barrel 51.This configuration allows the first holder 52 to move in the Z axisdirection without rotating with respect to the fixed frame 50. Theamount of movement of the first holder 52 with respect to the fixedframe 50 is determined by the shape of the first cam grooves 51 d.Female threads 52 c for attaching a conversion lens and an opticalfilter, such as a polarizing filter or a protective filter, are formedat the distal end of the first holder 52.

The second lens group support frame 54 is fixed to the second holder 55and supports the second lens group G2. The second lens group supportframe 54 and second holder 55 constitute the second lens group unit 77(an example of the first lens unit). The second holder 55 has threeconvex portions 55 b that are disposed at a constant pitch around theoptical axis AZ, and three cam pins 82 that are fixed to the convexportions 55 b. The cam pins 82 are inserted into the second cam grooves51 b. The convex portions 55 b are inserted into the linearthrough-grooves 50 c of the fixed frame 50. This configuration allowsthe second lens group support frame 54 and the second holder 55 to movein the Z axis direction without rotating with respect to the fixed frame50. The amount of movement of the second lens group support frame 54 andthe second holder 55 with respect to the fixed frame 50 is determined bythe shape of the second cam grooves 51 b.

The third lens group support frame 56 is a member that supports thethird lens group G3 (more precisely, the sixth lens L6 that functions asa focus lens), and has a bearing part 56 a, an anti-rotation part 56 b,a first rack support 56 c, second rack support 56 e, and a protrusion 56d. The sixth lens L6 and the third lens group support frame 56constitute the focus lens unit 75. The second holder 55 supports thefront ends of two guide poles 63 a and 63 b that extend in the Z axisdirection. A guide pole support plate 65 is a member for supporting therear end of the guide pole 63 a (an example of the guide shaft), and isfixed on the imaging sensor 11 side of the second holder 55. The guidepole 63 a is inserted into the bearing part 56 a, and the guide pole 63b is inserted into the anti-rotation part 56 b. The third lens groupsupport frame 56 is supported movably in the Z axis direction by theguide poles 63 a and 63 b while being restricted in rotation around theoptical axis AZ.

The first rack support 56 c and the second rack support 56 e areportions disposed on the Z axis direction negative side of the bearingcomponent 56 a, and support the rack 66 integrally movably in the axialdirection and rotatably around the rotational axis R2. Morespecifically, the rack 66 (an example of the transmission member) has abase 66 d disposed between the first rack support 56 c and the secondrack support 56 e, a rack body 66 a (an example of the transmissionmember body) disposed at the end of the base 66 d, and a shaft 66 b thatextends in the Z axis direction from the base 66 d. The base 66 d issmaller in the Z axis direction than the rack body 66 a.

The rack body 66 a is a portion that mates with a lead screw 64 a(discussed below), and has a plurality of teeth 66 c that mesh with thelead screw 64 a. The rack 66 converts the rotary motion of the leadscrew 64 a into linear motion in the Z axis direction. The rack body 66a is substantially in a U shape, and opens toward the opposite side fromthe rotational axis R2 (an example of the second rotational axis). Thedirection in which the rack body 66 a opens refers to the direction ofmovement of the lead screw 64 a when the lead screw 64 a is removed fromthe rack body 66 a, for example. In a state in which the drive unit 70(discussed below) is fixed to second holder 55, the rack body 66 a openssubstantially toward the circumferential direction.

The shaft 66 b is rotatably supported by the first rack support 56 c andthe second rack support 56 e. This allows the rack body 66 a to rotatewith respect to the third lens group support frame 56 around therotational axis R2.

Furthermore, as shown in FIGS. 9, 11, and 12, a torsion coil spring 68(an example of the elastic member) is disposed between the base 66 d andthe second rack support 56 e. The torsion coil spring 68 has a coiledpart 68 a that generates elastic force, a first end 68 b, and a secondend 68 c. The coiled part 68 a is placed over the shaft 66 b of the rack66. In a state in which the coiled part 68 a is twisted, the first end68 b is hooked onto the bearing component 56 a and the second racksupport 56 e, and the second end 68 c is hooked onto the rack body 66 aof the rack 66. The torsion coil spring 68 imparts rotational force inthe A direction to the rack 66. That is, the torsion coil spring 68imparts rotational force to the rack 66 so that the rack body 66 a movesto the outer peripheral side (the outside in the radial directionperpendicular to the optical axis AZ) with respect to the third lensgroup support frame 56. Since rotational force is imparted, the rack 66is always pressed against the lead screw 64 a. This reduces backlashbetween the rack 66 and the lead screw 64 a, and improves positionalaccuracy of the focus lens unit 75 with respect to the second lens groupunit 77. Also, since the rack 66 is always pressed against the leadscrew 64 a, drive force can be transmitted more efficiently from thelead screw 64 a to the rack 66.

Furthermore, the coiled part 68 a of the torsion coil spring 68 iscompressed in the Z axis direction (a direction parallel to therotational axis R2) between the second rack support 56 e and the base 66d. The torsion coil spring 68 imparts a pressing force F to the rack 66,and the rack 66 is pressed against the first rack support 56 c by thetorsion coil spring 68. This suppresses movement of the rack 66 in the Zaxis direction with respect to the third lens group support frame 56,and further improves positional accuracy of the focus lens unit 75.

The drive unit 70 is fixed to the second holder 55. The drive unit 70has a focus motor 64 (an example of an actuator) and a motor holder 64 c(an example of a support plate) that is fixed to the focus motor 64. Thefocus motor 64 is a stepping motor, for example. The focus motor 64 hasa motor body 64 g and a lead screw 64 a (an example of a drive shaft)that extends in the Z axis direction from the motor body 64 g. The motorbody 64 g rotates the lead screw 64 a around the rotational axis R1 (anexample of the first rotational axis) disposed parallel to the opticalaxis AZ. The motor holder 64 c is fixed to the focus motor 64, androtatably supports the lead screw 64 a. The rack 66 meshes with the leadscrew 64 a.

The protrusion 56 d is a portion for detecting the starting point of thefocus lens unit 75, and is provided at a location that can pass throughthe detection region of a photosensor 67 (discussed below). In thisembodiment, since the third lens group G3 (a focus lens group) is formedby the single sixth lens L6, the weight of the third lens group G3 canbe 1 g or less, for example, which allows the drive speed with the focusmotor 64 to be higher.

The fourth lens group support frame 61 has a first support frame 57, asecond support frame 58, a third support frame 59, and a fourth supportframe 60. The fourth lens group G4 and the fourth lens group supportframe 61 constitute a fourth lens group unit 78.

The first support frame 57 supports the seventh lens L7. The secondsupport frame 58 supports the eighth lens L8 and the ninth lens L9, andalso supports the first support frame 57 movably in two directionsperpendicular to the optical axis AZ. The second support frame 58 hasthree cam pins 80 that are disposed at a constant pitch around theoptical axis AZ.

The third support frame 59 supports the tenth lens L10 and the eleventhlens L11, and is fixed by screws, for example, to the second supportframe 58. The fourth support frame 60 supports the twelfth lens L12, andis fixed by screws, for example, to the third support frame 59. Becauseof their configuration, the first support frame 57, the second supportframe 58, the third support frame 59, and the fourth support frame 60move integrally along the optical axis AZ.

The first support frame 57 is supported by the second support frame 58so as to be movable in two directions perpendicular to the optical axisAZ, for example. This configuration allows the first support frame 57 tomove integrally in the Z axis direction with respect to the secondsupport frame 58, the third support frame 59, and the fourth supportframe 60, while allowing movement in a direction perpendicular to theoptical axis AZ.

The zoom ring unit 83 has a ring base 86, the zoom ring 84, and a linearposition sensor 87 that detects the rotational position of the zoom ring84. The “rotational position of the zoom ring 84” refers to the positionof the zoom ring 84 in the rotational direction, and can also beconsidered to be the rotational angle of the zoom ring 84 from areference position.

The zoom ring 84 has a cylindrical shape, and is supported by the ringbase 86 fixed to the fixed frame 50, so as to be movable around theoptical axis AZ in a state in which movement in the Z axis direction isrestricted. The zoom ring 84 has a through-hole 84 a at the end on the Zaxis direction negative side. A zoom drive pin 85 that is fixed to thecam barrel 51 is inserted into the through-hole 84 a. Consequently, thecam barrel 51 rotates integrally with the zoom ring 84 around theoptical axis AZ.

The linear position sensor 87 detects the rotational position androtational direction in which the user has put the zoom ring 84, andsends the detection result to the lens microcomputer 40. Morespecifically, the linear position sensor 87 is fixed to the ring base 86and has a slider 87 a that protrudes outward in the radial direction.This slider 87 a is inserted into a cam groove 84 b formed in the zoomring 84. When the zoom ring 84 is rotated with respect to the fixedframe 50, the slider 87 a moves in the Z axis direction along the camgroove 84 b. The linear position sensor 87 has a varistor, and when theslider 87 a sliders over a magnetic resistor that is inside thisvaristor, output (output voltage) that is proportional to the positionof the slider 87 a in the Z axis direction can be obtained linearlybetween terminals at both ends to which a specific voltage has beenapplied. The output of the linear position sensor 87 is converted intorotational position information, which allows the rotational position ofthe zoom ring 84 to be detected. The focal length of the optical systemL is displayed on the outer peripheral face of the zoom ring 84.

Since the first lens group G1 to fourth lens group G4 are mechanicallylinked via the lens support mechanism 71, the absolute positions of thefirst lens group G1 to fourth lens group G4 (such as their positionsusing a light receiving face 11 a of the imaging sensor 11 as areference) have a specific relationship to the rotational position ofthe zoom ring 84. Therefore, if the rotational position of the zoom ring84 is detected, the absolute positions of the first lens group G1 tofourth lens group G4 with respect to the lens mount 95 can beascertained. The zoom ring 84 may have another structure instead, suchas a movable lever.

The focus ring unit 88 has a focus ring 89 and a focus ring angledetector 90 that detects the rotational angle of the focus ring 89. Thefocus ring 89 has a cylindrical shape, and is supported by the ring base86 rotatably around the optical axis AZ in a state in which movement inthe Z axis direction is restricted. The rotational angle and rotationalposition of the focus ring 89 can be detected by the focus ring angledetector 90. The focus ring angle detector 90 has two photosensors (notshown), for example. The focus ring 89 has a plurality of protrusions 89a that protrude inward in the radial direction and are disposed atequidistant spacing in the rotational direction. Each of thesephotosensors has a light emitting part (not shown) and a light receivingpart (not shown), and the plurality of protrusions 89 a pass in betweenthe light emitting parts and the light receiving parts, allowing therotational angle and rotational direction of the focus ring 89 to bedetected. The focus ring 89 may have another structure instead, such asa movable lever.

(3) Focus Adjusting Unit

The focus adjusting unit 72 has the focus motor 64, a focus drivecontroller 41, and the photosensor 67. The focus motor 64 is fixed tothe second holder 55 and drives the focus lens unit 75 in the Z axisdirection with respect to the second lens group unit 77. The drive ofthe focus lens unit 75 with respect to the second lens group unit 77 isperformed by the focus motor 64 alone. In other words, in a state inwhich the focus motor 64 is not driving the focus lens unit 75 (such aswhen no power is being supplied to the focus motor 64), the focus lensunit 75 cannot be moved with respect to the second lens group unit 77.In this case, the focus lens unit 75 moves in the Z axis directionintegrally with the second holder 55.

The lead screw 64 a of the focus motor 64 rotates on the basis of adrive signal inputted from the focus drive controller 41. The rotarymotion generated by the focus motor 64 is converted by the lead screw 64a and the rack 66 into linear motion of the focus lens unit 75 in the Zaxis direction. Consequently, the focus lens unit 75 can move in the Zaxis direction with respect to the second lens group unit 77.

With this digital camera 1, to achieve a zoom lens system with which thefocal length can be varied while keeping the subject distancesubstantially constant, the focus lens unit 75 is driven by the focusadjusting unit 72 on the basis of a tracking table stored ahead of timein the lens microcomputer 40. This type of tracking is called electronictracking here.

The tracking table contains information indicating the position of thefocus lens unit 75 where the focused subject distance remainssubstantially constant even if the focal length changes (more precisely,the position of the focus lens unit 75 with respect to the second lensgroup unit 77). The phrase “the subject distance remains substantiallyconstant” means that the amount of change in the subject distance fallswithin a specific subject field depth. Electronic tracking will bediscussed below.

The photosensor 67, which detects the starting point position of thefocus lens unit 75, is installed in the second holder 55. Thisphotosensor 67 has a light emitting part (not shown) and a lightreceiving part (not shown). When the protrusion 56 d of the third lensgroup support frame 56 passes between the light emitting part and thelight receiving part, the photosensor 67 can detect the presence of theprotrusion 56 d. That is, the starting point position of the focus lensunit 75 with respect to the second lens group unit 77 can be detected bythe photosensor 67. In other words, the photosensor 67 is a startingpoint detector that detects the starting point position of the thirdlens group G3 with respect to the second lens group G2. The lensmicrocomputer 40 drives the third lens group G3 to the starting pointposition, and checks whether the focus lens unit 75 (the third lensgroup G3) is in the starting point position by using a signal from thephotosensor 67.

The starting point position that can be detected by the photosensor 67is an absolute position that never moves with respect to the second lensgroup unit 77. Accordingly, when the position of the focus lens unit 75is reset to the starting point position with respect to the second lensgroup unit 77, the photosensor 67 drives the focus lens unit 75 to theposition where the protrusion 56 d for starting point detection isdetected. When the power switch 25 is turned off, the focus lens unit 75is driven by the focus motor 64 to a position where the protrusion 56 dof the third lens group 56 is detected by the photosensor 67 regardlessof the position of focus lens unit 75, for example. Upon completion ofthe drive of the focus lens unit 75, the power supply to the digitalcamera 1 is halted. Conversely, when a power switch 25 of the digitalcamera 1 is turned on, the focus motor 64 drives the focus lens unit 75to a specific position determined on the basis of the tracking table.The starting point detector is not limited to being a photosensor, andmay instead be a combination of a magnet and a magnetic sensor, forexample.

(4) Aperture Adjusting Unit

The aperture adjusting unit 73 has the aperture unit 62 fixed to thesecond support frame 58, an aperture drive motor (not shown) that drivesthe aperture unit 62, and an aperture drive controller 42 that controlsthe aperture drive motor. The aperture drive motor is a stepping motor,for example. The aperture drive motor is driven on the basis of a drivesignal inputted from the aperture drive controller 42. The drive forcegenerated by the aperture drive motor drives aperture blades 62 a in theopening and closing directions. The aperture value of the optical systemL can be changed by driving the aperture blades 62 a.

(5) Blur Correction Unit

The blur correction unit 74 is for reducing blurring of the opticalimage attributable to movement of the interchangeable lens unit 2 andthe camera body 3, and has an electromagnetic actuator 46, a positiondetecting sensor 47, and a blur correction microcomputer 48.

The electromagnetic actuator 46 drives the first support frame 57 in adirection perpendicular to the optical axis AZ. More specifically, theelectromagnetic actuator 46 has a magnet (not shown) and a coil (notshown), for example. For instance, the coil is provided to the firstsupport frame 57, and the magnet is fixed to the second support frame58.

The position detecting sensor 47 is for detecting the position of thefirst support frame 57 with respect to the second support frame 58, andis a hole element, for example. A movement detecting sensor (not shown)such as a gyro sensor is installed in the interchangeable lens unit 2.The blur correction microcomputer 48 controls the electromagneticactuator 46 on the basis of the detection result of the positiondetecting sensor 47 and the detection result of the movement detectingsensor. Consequently, blurring of the optical image attributable tomovement of the digital camera 1 can be reduced.

Reducing blurring of the subject image may instead be accomplished byelectronic blur correction, in which blurring that appears in an imageis corrected on the basis of image data outputted from the imagingsensor 11. Also, blurring of the subject image may be reduced by asensor shift method in which the imaging sensor 11 is driven in twodirections perpendicular to the optical axis AZ.

(6) Lens Microcomputer

The lens microcomputer 40 has a CPU (not shown), a ROM (not shown), anda memory 40 a, and various functions can be performed by readingprograms stored in the ROM into the CPU. For instance, the lensmicrocomputer 40 can check whether the focus lens unit 75 is in thestarting point position by using a detection signal from the photosensor67.

The memory 40 a is a nonvolatile memory, and can hold stored informationeven when no power is being supplied. The memory 40 a contains atracking table (discussed below) for realizing a zoom lens system, orinformation related to the interchangeable lens unit 2 (lensinformation), for example. The lens microcomputer 40 controls the focusmotor 64, and the focus lens unit 75 is driven by the focus motor 64 inthe Z axis direction, on the basis of this tracking table. An operationin which the position of the focus lens unit 75 is made to conform tochanges in the focal length on the basis of a tracking table willhereinafter be referred to as electronic tracking.

The lens microcomputer 40 has a counter 40 b for counting the number ofpulses of the focus motor 64. The counter 40 b is set to a count of “+1”when the focus lens unit 75 is driven to the Z axis direction positiveside, and to a count of “−1” when the focus lens unit 75 is driven tothe Z axis direction negative side. The lens microcomputer 40 canascertain the relative position of the third lens group G3 with respectto the second lens group G2 (the position of the focus lens unit 75 withrespect to the second lens group unit 77) by thus counting the number ofdrive pulses of the focus motor 64.

For example, the rack 66 is driven by 0.6 mm in the Z axis direction forevery rotation of the lead screw 64 a of the focus motor 64. If thefocus motor 64, which has a 10-pole magnet, is driven by 1-2 phaseexcitation, then the rack 66 is driven in the Z axis direction by0.6/20/2=0.015 mm (15 μm) per pulse. During micro-step drive, the rack66 can be driven in even finer units. Using a stepping motor allows thefocus lens unit 75 to be driven in fine units, and reduces backlashduring reverse drive, for example. That is, selecting a stepping motoras the focus motor 64 affords very precise focus adjustment. Also,counting the number of drive pulses allows the current position of thefocus lens unit 75 with respect to the second lens group unit 77 to beascertained, and allows the amount of drive of the focus lens unit 75 tobe calculated.

Camera Body

The basic configuration of the camera body 3 will be described throughreference to FIGS. 1 to 4B. As shown in FIGS. 1 to 4B, the camera body 3has a case 3 a, a body mount 4, an operating unit 39, an imageacquisition unit 35, an image display unit 36, a viewfinder unit 38, abody microcomputer 10, and a battery 22.

(1) Case

The case 3 a constitutes the outer part of the camera body 3. As shownin FIGS. 4A and 4B, the body mount 4 is provided to the front face ofthe case 3 a, and the operating unit 39 is provided to the rear and topfaces of the case 3 a. More specifically, a display unit 20, the powerswitch 25, a mode selector dial 26, a navigation key 27, a menu settingbutton 28, a setting button 29, a capture mode selector button 34, and amoving picture capture operation button 24 are provided to the rear faceof the case 3 a. A shutter button 30 is provided to the top face of thecase 3 a.

(2) Body Mount

The body mount 4 is the portion of the interchangeable lens unit 2 wherethe lens mount 95 is mounted, and has a body-side contact (not shown)that can be electrically connected with the lens-side contact 91. Thecamera body 3 is able to send and receive data to and from theinterchangeable lens unit 2 via the body mount 4 and the lens mount 95.For example, the body microcomputer 10 (discussed below) sends the lensmicrocomputer 40 a control signal, such as an exposure synchronizationsignal, via the body mount 4 and the lens mount 95.

(3) Control Unit

As shown in FIGS. 4A and 4B, the operating unit 39 has various controlsthat the user can use to input operating information. For instance, thepower switch 25 is a switch for turning the power on and off to thedigital camera 1 or the camera body 3. When the power is turned on withthe power switch 25, power is supplied to the various parts of thecamera body 3 and the interchangeable lens unit 2.

The mode selector dial 26 is used to switch the operating mode, such asstill picture capture mode, moving picture capture mode, or reproductionmode, and the user can turn the mode selector dial 26 to switch theoperating mode. When the still picture capture mode is selected with themode selector dial 26, the operating mode is switched to the stillpicture capture mode, and when the moving picture capture mode isselected with the mode selector dial 26, the operating mode is switchedto the moving picture capture mode. In the moving picture capture mode,basically moving picture capture is possible. When the reproduction modeis selected with the mode selector dial 26, the operating mode isswitched to the reproduction mode, allowing the captured image to bedisplayed on the display unit 20.

The navigation key 27 is used to select the left, right, up, and downdirections. The user can use the navigation key 27 to select the desiredmenu from various menu screens displayed on the display unit 20, forexample. The menu setting button 28 is for setting the variousoperations of the digital camera 1. The setting button 29 is forexecuting the operations of the various menus.

The moving picture capture operation button 24 is for starting andstopping the capture of moving pictures. Even if the operating modeselected with the mode selector dial 26 is the still picture capturemode or the reproduction mode, when the moving picture capture operationbutton 24 is pressed, the operating mode is forcibly changed to themoving picture capture mode, and moving picture capture begins,regardless of the setting on the mode selector dial 26. When this movingpicture capture operation button 24 is pressed during the capture of amoving picture, the moving picture capture ends and the operating modechanges to the one selected on the mode selector dial 26, that is, tothe one prior to the start of moving picture capture. For example, ifthe still picture capture mode has been selected with the mode selectordial 26 when the moving picture capture operation button 24 is pressed,the operating mode automatically changes to the still picture capturemode after the moving picture capture operation button 24 is pressedagain.

The shutter button 30 is pressed by the user to capture an image. Whenthe shutter button 30 is pressed, a timing signal is outputted to thebody microcomputer 10. The shutter button 30 is a two-stage switch thatcan be pressed half way down or all the way down. Light measurement andranging are commenced when the user presses the button half way down.When the user presses the shutter button 30 all the way down in a statein which the shutter button 30 has been pressed half way down, a timingsignal is outputted, and image data is acquired by the image acquisitionunit 35.

As shown in FIG. 2, a lens attachment button 99 for attaching andremoving the interchangeable lens unit 2 to and from the camera body 3is provided to the front face of the camera body 3. The lens attachmentbutton 99 has a contact (not shown) that is in its “on” state when thebutton is pressed by the user, for example, and is electricallyconnected to the body microcomputer 10. When the lens attachment button99 is pressed, the built-in contact is switched on, and the bodymicrocomputer 10 recognizes that the lens attachment button 99 has beenpressed.

(4) Image Acquisition Unit

The image acquisition unit 35 mainly comprises the imaging sensor 11such as a CCD (Charge Coupled Device) that performs opto-electricalconversion, a shutter unit 33 that adjusts the exposure state of theimaging sensor 11, a shutter controller 31 that controls the drive ofthe shutter unit 33 on the basis of a control signal from the bodymicrocomputer 10, and an imaging sensor drive controller 12 thatcontrols the operation of the imaging sensor 11.

The imaging sensor 11 is a CCD (Charge Coupled Device) sensor, forexample, that converts the optical image formed by the optical system Linto an electrical signal. The imaging sensor 11 is driven andcontrolled on the basis of timing signals generated by the imagingsensor drive controller 12. The imaging sensor 11 may instead be a CMOS(Complementary Metal Oxide Semiconductor) sensor.

The shutter controller 31 drives a shutter drive actuator 32 andoperates the shutter unit 33 according to a control signal outputtedfrom the body microcomputer 10 that has received a timing signal.

The auto-focusing method that is employed in this embodiment is acontrast detection method that makes use of image data produced by theimaging sensor 11. Using a contrast detection method allowshigh-precision focal adjustment.

(5) Body Microcomputer

The body microcomputer 10 is a control device that is the command centerof the camera body 3, and controls the various components of the digitalcamera 1 according to operation information inputted to the operationunit 39. More specifically, the body microcomputer 10 is equipped with aCPU, ROM, and RAM, and the programs held in the ROM are read by the CPU,allowing the body microcomputer 10 to perform a variety of functions.For instance, the body microcomputer 10 has the function of detectingthat the interchangeable lens unit 2 has been mounted to the camera body3, or the function of acquiring information about controlling thedigital camera 1, such as information about the focal length from theinterchangeable lens unit 2.

The body microcomputer 10 is able to receive signals from the powerswitch 25, the shutter button 30, the mode selector dial 26, thenavigation key 27, the menu setting button 28, and the setting button29. Various information related to the camera body 3 is held in a memory10 a inside the body microcomputer 10. The memory 10 a is a nonvolatilememory, and can hold stored information even when no power is beingsupplied.

Also, the body microcomputer 10 periodically produces a verticalsynchronization signal, and produces an exposure synchronization signalon the basis of the vertical synchronization signal in parallel with theproduction of the vertical synchronization signal. The bodymicrocomputer 10 can produce an exposure synchronization signal, sincethe body microcomputer 10 ascertains beforehand the exposure starttiming and the exposure stop timing based on the verticalsynchronization signal. The body microcomputer 10 outputs a verticalsynchronization signal to a timing generator (not shown), and outputs anexposure synchronization signal at a specific period to the lensmicrocomputer 40 via the body mount 4 and the lens mount 95. The lensmicrocomputer 40 acquires position information about the focus lens unit75.

The imaging sensor drive controller 12 produces an electronic shutterdrive signal and a read signal of the imaging sensor 11 at a specificperiod on the basis of the vertical synchronization signal. The imagingsensor drive controller 12 drives the imaging sensor 11 on the basis ofthe electronic shutter drive signal and the read signal. That is, theimaging sensor 11 reads to a vertical transfer part (not shown) theimage data produced by numerous opto-electrical conversion element (notshown) present in the imaging sensor 11, according to the read signal.

The body microcomputer 10 also controls the focus adjusting unit 72(discussed below) via the lens microcomputer 40.

The image signal outputted from the imaging sensor 11 is sent from ananalog signal processor 13 and successively processed by an A/Dconverter 14, a digital signal processor 15, a buffer memory 16, and animage compressor 17. The analog signal processor 13 subjects the imagesignal outputted from the imaging sensor 11 to gamma processing or othersuch analog signal processing. The A/D converter 14 converts the analogsignal outputted from the analog signal processor 13 into a digitalsignal. The digital signal processor 15 subjects the image signalconverted into a digital signal by the A/D converter 14 to digitalsignal processing such as noise elimination or contour enhancement. Thebuffer memory 16 is a RAM (Random Access Memory), and temporarily storesthe image signal. The image signal stored in the buffer memory 16 issent to and processed by first the image compressor 17 and then an imagerecorder 18. The image signal stored in the buffer memory 16 is read ata command from an image recording controller 19 and sent to the imagecompressor 17. The data of the image signal sent to the image compressor17 is compressed into an image signal according to a command from theimage recording controller 19. This compression adjusts the image signalto a smaller data size than that of the original data. An example of themethod for compressing the image signal is the JPEG (Joint PhotographicExperts Group) method in which compression is performed on the imagesignal for each frame. After this, the compressed image signal isrecorded by the image recording controller 19 to the image recorder 18.When a moving picture is recorded, JEPG was used to compress a pluralityof image signals, compressing an image signal for each frame, and an H.264/AVC method can also be used, in which compression is performed onimage signals for a plurality of frames all at once.

The image recorder 18 produces a still picture file or moving picturefile that is associated with specific information to be recorded withthe image signal. The image recorder 18 also records the still picturefile or moving picture file on the basis of a command from the imagerecording controller 19. The image recorder 18 is a removable memoryand/or an internal memory, for example. The specific information to berecorded with the image signal includes the date the image was captured,focal length information, shutter speed information, aperture valueinformation, and photography mode information. Still picture files arein Exif (TRADEMARK) format or a format similar to Exif (TRADEMARK)format. Moving picture files are in H. 264/AVC format or a formatsimilar to H. 264/AVC format.

(6) Image Display Unit

The image display unit 36 has the display unit 20 and an image displaycontroller 21. The display unit 20 is a liquid crystal monitor, forexample. The display unit 20 displays as a visible image the imagesignal recorded to the buffer memory 16 or the image recorder 18 on thebasis of a command from the image display controller 21. Possibledisplay modes on the display unit 20 include a display mode in whichonly the image signal is displayed as a visible image, and a displaymode in which the image signal and information from the time of captureare displayed as a visible image.

(7) Viewfinder

The viewfinder unit 38 has a liquid crystal viewfinder 8 that displaysthe image acquired by the imaging sensor 11, and a viewfinder eyepiecewindow 9 provided to the rear face of the case 3 a. The user looks intothe viewfinder eyepiece window 9 to view the image displayed on theliquid crystal viewfinder 8.

(8) Battery

The battery 22 supplies power to the various components of the camerabody 3, and also supplies power to the interchangeable lens unit 2 viathe lens mount 95. In this embodiment, the battery 22 is a rechargeablebattery. The battery 22 may be a dry cell, or may be an external powersupply, with which power is supplied from the outside through a powercord.

Tracking Table

With the digital camera 1, electronic tracking is performed by the focusadjusting unit 72 so that the focal length can be varied while thesubject distance is kept substantially constant. More specifically, asshown in FIG. 15, to perform electronic tracking, a tracking table 100is held in the memory 40 a. This tracking table 100 shows therelationship between the rotational position of the zoom ring 84 and theposition of the focus lens unit 75 in the Z axis direction with respectto the second lens group unit 77. For example, the memory 40 a holdsthree tracking tables 100 corresponding to subject distances of 0.3 m,1.0 m, and infinity (∞).

The tracking table 100 consists of discrete information in which therotational position of the zoom ring 84 and the position of the focuslens unit 75 in the Z axis direction are divided into several groups. Ingeneral, the number of divisions is determined so that the subjectdistance will fit within a specific subject field depth even if the zoomring 84 is turned.

The rotational position of the zoom ring 84 (position in the rotationaldirection) can be detected by the linear position sensor 87. On thebasis of this detection result and the tracking table 100, the lensmicrocomputer 40 can determine the position of the focus lens unit 75 inthe Z axis direction with respect to the second lens group unit 77.

The starting point position D of the focus lens unit 75 with respect tothe second lens group unit 77 is detected by the photosensor 67, whichis indicated by the one-dot chain line in FIG. 15. In this embodiment,the starting point position D is located near the center of the movementrange of the focus lens unit 75 (between positions E1 and E2) in theinfinity tracking table 100. Thus disposing the starting point positionD near the center allows the focus lens unit 75 to be moved relativelyquickly to any position when the power is turned on to the digitalcamera 1.

The reason the starting point position D is determined using theinfinity tracking table 100 as a reference is that there is a higherprobability of capturing the subject at the infinity position when theuser turns on the power to the digital camera 1 to photograph thesubject.

The tracking table 100 may also be expressed by a polynomial, ratherthan discrete information divided into several groups. Positioninformation about the first lens group G1, second lens group G2, orfourth lens group G4 in the Z axis direction may also be used instead ofthe rotational position of the zoom ring 84. The “position of the focuslens unit 75 in the Z axis direction with respect to the second lensgroup unit 77” can be rephrased as the position of the third lens groupG3 in the Z axis direction with respect to the second lens group unit77, or the position of the third lens group G3 in the Z axis directionwith respect to the second lens group G2.

Layout of Drive Unit

This digital camera 1 is characterized by the layout of the drive unit70. The layout of the drive unit 70 will be described through referenceto FIGS. 9, 10, 16, and 17. FIG. 16 is a plan view of the focus lensunit 75. FIG. 17 is a plan view of the focus lens unit 75 when the driveunit 70 is attached. FIGS. 16 and 17 are plan views of when the focuslens unit 75 is viewed from the Z axis direction negative side.

As shown in FIG. 16, the drive unit 70 is fixed to the second lens groupunit 77 so that a profile line formed by the second lens group unit 77and the drive unit 70 when viewed in a direction along the optical axisAZ will be substantially circular. More specifically, the drive unit 70is fixed to the second holder 55 so that a first profile line 70L formedby the second holder 55 and the drive unit 70 is substantially circular.The first profile line 70L formed by the second holder 55 and the driveunit 70 substantially follows the inner peripheral face 50L of the fixedframe 50 when viewed in the Z axis direction.

Here, in determining the first profile line 70L, portions that protrudeto the outside in order to come into contact with another member (thefixed frame 50 and the cam barrel 51 here), such as the cam pin 82 andthe protrusion 55 b, are not taken into account.

The motor holder 64 c of the drive unit 70 is fixed to the second holder55 so as to face the third lens group G3. More precisely, the secondholder 55 has a first support 55 a, a second support 55 d, an opening 55e, and a holder 55 c. The first support 55 a is a portion that sticksout in the Z axis direction, and supports the holder body 64 e. Thesecond support 55 d is a portion that sticks out in the Z axisdirection, and the holder body 64 e is fixed with screws 69.

The first support 55 a and the second support 55 d are disposed with aspace in the circumferential direction around the optical axis AZ (suchas the C direction shown in FIG. 16). The circumferential directionreferred to here is a direction that follows an arc around the opticalaxis AZ. The opening 55 e is formed between the first support 55 a andthe second support 55 d. The lead screw 64 a of the focus motor 64 isdisposed in this opening 55 e. The motor body 64 g of the focus motor 64is held in the holder 55 c. The drive unit 70 has four terminals 64 f towhich power is supplied. As shown in FIG. 16, the terminals 64 f stickout from the motor body 64 g of the focus motor 64 in the approximatecircumferential direction. More precisely, the terminals 64 f stick outon the opposite side from the rotational axis R2 with respect to therotational axis R1. This makes it easy to ensure enough space to holdthe electrical wiring connected to the terminals 64 f.

The motor holder 64 c has the flat holder body 64 e that extendssubstantially parallel to the rotational axis R1. For instance, animaginary line N that is perpendicular to the holder body 64 e andintersects the rotational axis R1 overlaps the third lens group G3 whenviewed in the Z axis direction. In this embodiment, the imaginary line Nintersects the optical axis AZ. The imaginary line N is perpendicular toa plane M parallel to the holder body 64 e.

The rack body 66 a opens substantially toward the circumferentialdirection in a state in which the drive unit 70 is fixed to the secondholder 55. The torsion coil spring 68 imparts rotational force to therack 66 so that the rack body 66 a rotates around the rotational axis R2facing outside of the second holder 55. Accordingly, as shown in FIG.17, in a state in which the drive unit 70 is not fixed to the secondholder 55, the rack body 66 a is pressed against the first support 55 aof the second holder 55 by the torsion coil spring 68. In this state,the rack 66 is stationary with respect to the second holder 55.Accordingly, since the rack body 66 a is stationary with respect to thesecond holder 55 in a state of facing outward more than in thecircumferential direction, when the drive unit 70 is assembled, it iseasier to attach the lead screw 64 a to the rack body 66 a. As shown inFIG. 17, the second holder 55 has the first support 55 a and the secondsupport 55 d. The motor holder 64 c is fixed to the second support 55 dby the two screws 69. The first support 55 a supports the motor holder64 c. The opening 55 e is formed between the first support 55 a and thesecond support 55 d in the circumferential direction. The holder 55 c inwhich the focus motor 64 is held is formed on the Z axis directionpositive side of the opening 55 e.

As shown in FIG. 16, the drive unit 70, the rotational axis R2, and theguide pole 63 a are disposed aligned in the circumferential direction.More specifically, the drive unit 70 is aligned with the rotational axisR2 in the circumferential direction, and the rotational axis R2 isaligned with the guide pole 63 a in the circumferential direction. Thelead screw 64 a is aligned with the rotational axis R2 in thecircumferential direction. Accordingly, the rack body 66 a is disposedso as to open substantially in the circumferential direction. Therotational axis R2 is disposed between the drive unit 70 and the guidepole 63 a in the circumferential direction.

The rotational axis R1, the rotational axis R2, and the center R3 of theguide pole 63 a are disposed at substantially the same position in theradial direction. In other words, the rotational axis R1, the rotationalaxis R2, and the center R3 are disposed on substantially the samecircumference.

Assembly Work

The work of assembling the second lens group unit 77, the focus lensunit 75, and the drive unit 70 will now be described.

The assembly of the second lens group unit 77 is performed, and theguide poles 63 a and 63 b are fixed to the second holder 55 of thesecond lens group unit 77.

Next, the assembly of the focus lens unit 75 is performed. Morespecifically, the third lens group G3 is fixed to the third lens groupsupport frame 56. The shaft 66 b of the rack 66 is inserted into thetorsion coil spring 68, and in this state the rack 66 is attached to thefirst rack support 56 c and the second rack support 56 e.

After the assembly of the focus lens unit 75, the focus lens unit 75 isattached to the guide poles 63 a and 63 b. More specifically, the guidepole 63 a is inserted into the bearing component 56 a, and the guidepole 63 b is inserted into the anti-rotation component 56 b. The focuslens unit 75 is slide along the guide poles 63 a and 63 b until the rack66 is disposed within the opening 55 e of the second holder 55.

As shown in FIG. 17, since the rack 66 is pushed in the A direction withrespect to the third lens group support frame 56 by the elastic force ofthe torsion coil spring 68, the rack 66 is pressed against the firstsupport 55 a by the torsion coil spring 68 and does not fall inside (thethird lens group G3 side; in the opposite direction from the Adirection). In this state, the rack body 66 a of the rack 66 is disposedin the opening 55 e, and the rack body 66 a opens outward more than inthe circumferential direction.

After the focus lens unit 75 has been attached to the second lens groupunit 77, as shown in FIG. 17, the drive unit 70 is attached from theoutside of the second holder 55. At this point, the rack body 66 a opensfacing outward in a state of being disposed in the opening 55 e, so evenif the drive unit 70 is attached substantially facing inward in theradial direction (toward the optical axis AZ), the lead screw 64 a canbe mated relatively easily with the rack body 66 a.

In a state in which the lead screw 64 a is mated to the rack body 66 a,the motor holder 64 c is pushed against the first support 55 a and thesecond support 55 d. In this state, the motor holder 64 c is fixed tothe second support 55 d by the screws 69, and the second lens group unit77, the focus lens unit 75, and the drive unit 70 are in the assemblystate shown in FIG. 16.

Thus, the size can be reduced and the drive unit 70 can be easilyassembled by using the torsion coil spring 68 and changing the directionin which the rack body 66 a faces more to the outside than in thecircumferential direction during assembly.

Operation of the Digital Camera

The operation of the digital camera 1 will be described.

(1) Imaging Mode

This digital camera 1 has two imaging modes. More specifically, thedigital camera 1 has a viewfinder imaging mode in which the user looksthrough the viewfinder eyepiece window 9 to view the subject, and amonitor imaging mode in which the user observes the subject on thedisplay unit 20.

With the viewfinder imaging mode, the image display controller 21 drivesthe liquid crystal viewfinder 8, for example. As a result, an image ofthe subject (a so-called through-image) acquired by the imaging sensor11 is displayed on the liquid crystal viewfinder 8.

With the monitor imaging mode, the display unit 20 is driven by theimage display controller 21, for example, and a real-time image of thesubject is displayed on the display unit 20. Switching between these twoimaging modes can be performed with the capture mode selector button 34.

(2) Zoom Operation

Next, the operation of the interchangeable lens unit 2 when the userperforms zooming will be described.

When the user rotates the zoom ring 84, the cam barrel 51 rotates alongwith the zoom ring 84. When the cam barrel 51 rotates around the opticalaxis AZ, the first holder 52 is guided by the first cam grooves 51 d ofthe cam barrel 51, and advances in the Z axis direction. The secondholder 55 and the fourth lens group support frame 61 are also guided bythe second cam grooves 51 b and the third cam grooves 51 c of the cambarrel 51, and advance in the Z axis direction. Thus, by rotating thezoom ring 84, the state of the interchangeable lens unit 2 can bechanged from the wide angle end state shown in FIGS. 5 and 6 to thetelephoto end state shown in FIGS. 7 and 8. Consequently, the subjectcan be imaged at the desired zoom position by adjusting the rotationalposition of the zoom ring 84.

The second holder 55 is mechanically driven in the Z axis direction byrotating the zoom ring 84 here, but only the focus lens unit 75 iselectrically driven and controlled by the focus adjusting unit 72 on thebasis of the tracking table 100 stored ahead of time in the memory 40 a,so that the subject distance remains substantially constant. Forexample, when the focus lens unit 75 is driven by the focus motor 64 onthe basis of the tracking table 100, the focal state can be kept atinfinity both when the move is from the wide angle end to the telephotoend, and when the move is from the telephoto end to the wide angle end.

More precisely, when the zoom ring 84 is turned, the first lens groupG1, the second lens group G2, the third lens group G3, and the fourthlens group G4 move in the Z axis direction along the optical axis AZ.Consequently, the magnification of the subject image changes. At thispoint the third lens group G3 also moves in the Z axis direction alongthe optical axis AZ in a state of being supported by the second holder55 via the third lens group support frame 56. When there is a relativechange in the positional relationship of the first lens group G1, thesecond lens group G2, the third lens group G3, and the fourth lens groupG4, the focal state of the subject image formed on the imaging sensor 11also changes. That is, the subject distance at which the focal point isformed on the imaging sensor 11 changes.

In view of this, with the digital camera 1, even if the focal lengthchanges, the subject distance can be kept substantially constant bydriving the focus motor 64 according to the rotational position of thezoom ring 84. More specifically, using just the focus motor 64, thefocus lens unit 75 including the third lens group G3 is driven withrespect to the second lens group unit 77. The lens microcomputer 40acquires the rotational position of the zoom ring 84 on the basis of thedetection signal of the linear position sensor 87. At the same time, thelens microcomputer 40 calculates the position of the focus lens unit 75with respect to the second lens group unit 77 from the count value atthe counter 40 b. Utilizing the plurality of tracking tables 100 shownin FIG. 15, the lens microcomputer 40 finds the current subject distancefrom these two pieces of information (the current rotational position ofthe zoom ring 84, and the position of the focus lens unit 75 withrespect to the second lens group unit 77), and selects the trackingtable 100 corresponding to the subject distance thus found. Here, wewill assume that the tracking table 100 corresponding to infinity wasselected.

Next, the lens microcomputer 40 again acquires the rotational positionof the zoom ring 84, and finds the rotational speed of the zoom ring 84,that is, the rate of change in the focal length, from the amount ofchange in the rotational position of the zoom ring 84.

Next, the lens microcomputer 40 predicts the rotational position of thezoom ring 84 after the elapse of a specific time from the currentrotational angle of the zoom ring 84 and the rotational speed of thezoom ring 84, and finds as a target position the position of the focuslens unit 75 in the Z axis direction corresponding to the predictedrotational position of the zoom ring 84. After the elapse of a specifictime, the lens microcomputer 40 drives the focus motor 64 via the focusdrive controller 41 so that the focus lens unit 75 will be located atthis target position. Consequently, the focus lens unit 75 is driven soas to follow the movement of the other lens groups, and the subjectdistance is kept constant.

Thus, in the electronic tracking operation, the lens microcomputer 40predicts the change in the focal length that will accompany zoomingoperation, and acquires from the tracking table 100 the target positionof the focus lens unit 75 corresponding to the predicted focal length.The focus lens unit 75 is driven to the target position by the focusmotor 64 in parallel with the zooming operation of the optical system L.Since this operation is executed at specific time intervals, even if thezoom ring 84 is rotated and the focal length of the optical system Lchanges, the focus lens unit 75 will move to the Z axis directionposition corresponding to the focal length on the basis of the trackingtable 100, and the drive of the focus lens unit 75 can conform to thechange in the focal length. Consequently, the subject distance can bekept substantially constant regardless of any change in the focallength. The control of these components may be performed by the bodymicrocomputer 10, rather than lens microcomputer 40.

Similarly, when the focused subject distance is short, such as 1 m, forexample, the tracking table 100 for which the subject distance is 1 m isselected, and both when the move is from the wide angle end to thetelephoto end, and when the move is from the telephoto end to the wideangle end, the focused state at a short distance can be maintained bydriving the focus motor 64, and the zooming operation can be carried outsmoothly.

In particular, since the focus lens unit 75 and the focus motor 64 movein the Z axis direction integrally with the second lens group unit 77,even if the user turns the zoom ring 84 quickly, the focus lens unit 75can still be moved integrally with the second lens group unit 77.Therefore, if the subject distance is to be kept substantially constantbefore and after the zooming operation, the focus motor 64 may move thethird lens group G3 by a distance obtained by subtracting the distancethat the second lens group G2 is moved by the cam mechanism with respectto the imaging sensor 11 from the distance that the third lens group G3is to be moved with respect to the imaging sensor 11. This makes it easyto keep up with fast operation of the zoom ring 84 by the user.

Also, in this embodiment, if a zooming operation is performed from thewide angle end to the telephoto end, with the subject distance atinfinity, the focus lens unit 75 (more precisely, the third lens groupG3, which is a focus lens group) must be moved in the Z axis directionby about 3 mm with respect to the imaging sensor 11. When the focusmotor 64 is driven at 800 pps, the amount of drive of the focus lensunit 75 per rotation of the focus motor 64 is 0.6 mm as mentioned above,so it takes 0.25 second to move the focus lens unit 75 by 3 mm in the Zaxis direction on the basis of the tracking table. Since it is possibleto move the focus lens unit 75 from the wide angle end to the telephotoend in approximately 0.25 second, even if the user should turn the zoomring 84 from the wide angle end to the telephoto end in 0.5 second, thedrive of the focus lens unit 75 can keep up with the change in focallength. Consequently, even if the user should perform a quick zoomingoperation while looking at the subject on the display unit 20 in livepreview mode, for example, the subject image that shows on the displayunit 20 will be unlikely to be blurred, and this makes the camera easierto use.

(3) Focusing Operation

Next, the focusing operation of the digital camera 1 will be described.The digital camera 1 has two focus modes: an auto-focus imaging mode anda manual imaging mode. The user of the digital camera 1 can select thefocus mode with a focus imaging mode setting button (not shown) providedto the camera body 3.

In the auto-focus imaging mode, auto-focus operation is performed bycontrast detection method. When auto-focusing is performed by contrastdetection method, the body microcomputer 10 asks the lens microcomputer40 for contrast AF data. This contrast AF data is necessary inauto-focusing by contrast detection method, and includes, for example,the focus drive speed, focus shift amount, image magnification ratio,and information about whether contrast AF is possible.

The body microcomputer 10 monitors whether or not the shutter button 30has been pressed half way down. If the shutter button 30 has beenpressed half way down, the body microcomputer 10 issues an auto-focuscommencement command to the lens microcomputer 40. This auto-focuscommencement command is to start the auto-focus operation by contrastdetection method. Upon receiving this command, the lens microcomputer 40drives and controls the focus motor 64, which is a focus actuator. Moreprecisely, the lens microcomputer 40 sends a control signal to the focusdrive controller 41. On the basis of this control signal, the focusdrive controller 41 drives the focus motor 64, and the focus lens unit75 moves minutely.

The body microcomputer 10 calculates an evaluation value for auto-focusoperation (hereinafter referred to as an AF evaluation value) on thebasis of the received image data. More specifically, the bodymicrocomputer 10 sends a command to the digital signal processor 15. Thedigital signal processor 15 sends an image signal to the bodymicrocomputer 10 at a specific timing on the basis of the receivedcommand. The body microcomputer 10 finds a brightness signal from theimage data produced by the imaging sensor 11, and finds the AFevaluation value by integrating the high-frequency component within thescreen of the brightness signal. The AF evaluation value thus calculatedis stored in a DRAM (not shown) in a state of being associated with theexposure synchronization signal. Since the lens position informationacquired by the body microcomputer 10 from the lens microcomputer 40 isalso associated with the exposure synchronization signal, the bodymicrocomputer 10 can store the AF evaluation value with it associatedwith the lens position information.

Next, the body microcomputer 10 extracts as the focal point the positionof the focus lens unit 75 where the AF evaluation value is at itsmaximum, on the basis of the AF evaluation value stored in the DRAM. Themethod for driving the focus lens unit 75 in the extraction of the focalpoint is generally known as a hill climbing method. With a hill climbingmethod, the focus lens unit 75 is moved in the direction of increasingthe AF evaluation value, and the AF evaluation value is found for eachposition of the focus lens unit 75. This operation is continued untilthe maximum value for the AF evaluation value is detected, that is,until the AF evaluation value increases up to its peak and begins todecrease.

The body microcomputer 10 sends a control signal to the focus drivecontroller 41 via the lens microcomputer 40 so that the focus lens unit75 will be driven to the position corresponding to the extracted focalpoint. The focus drive controller 41 produces a drive pulse for drivingthe focus motor 64 on the basis of a control signal from the bodymicrocomputer 10 (or the lens microcomputer 40), for example. The focusmotor 64 is driven by an amount corresponding to this drive signal, andthe focus lens unit 75 moves in the Z axis direction to the positioncorresponding to the focal point.

Focusing in auto-focus imaging mode is performed in this way with thedigital camera 1. The above operation is executed instantly when theuser presses the shutter button 30 half way down.

Focusing by contrast detection method can also be carried out in monitorimaging mode (known as live preview mode), in which real-time image datacan be produced with the imaging sensor 11. The reason for this is thatin live preview mode, image data is produced in a steady state by theimaging sensor 11, and auto-focusing by contrast detection method usingthis image data is easy.

In live preview mode, since a real-time image of the subject isdisplayed on the display unit 20, the user can decide on the compositionfor taking the still picture or moving picture while looking at thedisplay unit 20. Also, there is another imaging mode the user can selectin addition to live preview mode using the display unit 20, which is asecond live preview mode (viewfinder imaging mode) in which the subjectimage from the interchangeable lens unit 2 is guided to the liquidcrystal viewfinder 8 (viewfinder unit 38).

The manual focus imaging mode will now be described.

When the user turns the focus ring 89, the focus ring angle detector 90detects the rotational angle of the focus ring 89 and outputs a signalcorresponding to this rotational angle. The focus drive controller 41 isable to receive signals from the focus ring angle detector 90, and ableto send signals to the focus motor 64. The focus drive controller 41sends the decision result to the lens microcomputer 40. The focus drivecontroller 41 drives the focus motor 64 on the basis of a control signalfrom the lens microcomputer 40. More precisely, the lens microcomputer40 produces a drive signal for driving the focus motor 64 on the basisof a focus ring rotational angle signal. When the lead screw 64 a of thefocus motor 64 rotates according to the drive signal, the focus lensunit 75 moves in the Z axis direction via the rack 66 that meshes withthe lead screw 64 a. In the wide angle end state shown in FIGS. 5 and 6,the subject distance is infinity, but as the subject distance drawscloser, the focus lens unit 75 moves to the Z axis direction positiveside. Similarly, in the telephoto end state shown in FIGS. 7 and 8, thesubject distance is infinity, but as the subject distance becomesshorter, the focus lens unit 75 moves to the Z axis direction positiveside. The amount of movement of the focus lens unit 75 is greater inthis case than in the case of the wide angle end.

In this way, the user can perform focusing by turning the focus ring 89while looking at the subject on the display unit 20. In the manual focusimaging mode, when the user presses the shutter button 30 all the waydown, imaging is performed in this unchanged state.

(4) Still Picture Capture

When the user presses the shutter button 30 all the way down, a commandis sent from the body microcomputer 10 to the lens microcomputer 40 sothat the aperture value of the optical system L will be set to theaperture value calculated on the basis of the light measurement outputof the imaging sensor 11. The aperture drive controller 42 is controlledby the lens microcomputer 40, and the aperture unit 62 is constricted tothe indicated aperture value. Simultaneously with the indication of theaperture value, a drive command is sent from the imaging sensor drivecontroller 12 to the imaging sensor 11, and a shutter unit 33 drivecommand is sent out. The imaging sensor 11 is exposed by the shutterunit 33 for a length of time corresponding to the shutter speedcalculated on the basis of the light measurement output of the imagingsensor 11.

The body microcomputer 10 executes imaging processing and, when theimaging is completed, sends a command signal to the image recordingcontroller 19. The image recorder 18 records an image signal to aninternal memory and/or removable memory on the basis of the command ofthe image recording controller 19. The image recorder 18 records imagingmode information (whether auto-focus imaging mode or manual focusimaging mode) along with the image signal to the internal memory and/orremovable memory on the basis of the command of the image recordingcontroller 19.

Upon completion of the exposure, the imaging sensor drive controller 12reads image data from the imaging sensor 11, and after specific imageprocessing, image data is outputted via the body microcomputer 10 to theimage display controller 21. Consequently, the captured image isdisplayed on the display unit 20.

Also, upon completion of the exposure, the shutter unit 33 is reset toits initial position by the body microcomputer 10. The bodymicrocomputer 10 issues a command to the lens microcomputer 40 for theaperture drive controller 42 to reset the aperture unit 62 to its openposition, and a reset command is sent from the lens microcomputer 40 tothe various units. Upon completion of this resetting, the lensmicrocomputer 40 tells the body microcomputer 10 that resetting iscomplete. After the resetting completion information has been receivedfrom the lens microcomputer 40, and after a series of post-exposureprocessing has been completed, the body microcomputer 10 confirms thatthe shutter button 30 is not being pressed, and the imaging sequence isconcluded.

(5) Moving Picture Capture

The digital camera 1 also has the function of capturing moving pictures.In moving picture imaging mode, image data is produced by the imagingsensor 11 at a specific period, and the image data thus produced isutilized to continuously carry out auto-focusing by contrast detectionmethod. In moving picture imaging mode, if the shutter button 30 ispressed, or if the moving picture capture operation button 24 ispressed, a moving picture is recorded to the image recorder 18, and whenthe shutter button 30 or the moving picture capture operation button 24is pressed again, recording of the moving picture by the image recorder18 is stopped.

Features of Digital Camera

The features of the digital camera 1 described above are as follows.

(1)

With this digital camera 1, when viewed in the Z axis direction, thedrive unit 70 is fixed to the second lens group unit 77 so that thefirst profile line 70L formed by the second lens group unit 77 and thedrive unit 70 will be substantially circular, and this reduces how muchthe drive unit 70 sticks out from the second lens group unit 77.Consequently, the interchangeable lens unit 2 can be more compact.

(2)

The motor holder 64 c of the drive unit 70 is fixed to the second holder55 so as to face the third lens group G3. More precisely, since themotor holder 64 c is disposed facing the optical axis AZ (the center ofthe third lens group G3), the profile of the second lens group unit 77and the drive unit 70 can be made to be closer to circular.

In particular, with this digital camera 1, an imaginary line N that isperpendicular to the holder body 64 e and intersects the rotational axisR1 overlaps the third lens group G3 when viewed in the Z axis direction.The imaginary line N also intersects the optical axis AZ. Thisconfiguration reduces how much the drive unit 70 sticks out from theprofile of the second lens group unit 77, and allows the first profileline 70L formed by the second lens group unit 77 and the drive unit 70to be closer to circular.

(3)

In a state in which the drive unit 70 is fixed to the second lens groupunit 77, the rack body 66 a opens substantially toward thecircumferential direction, so the drive unit 70 and the rack 66 can beefficiently disposed on the outer peripheral side of the third lensgroup G3.

(4)

A rotational force is imparted by the torsion coil spring 68 to the rack66 so that the rack body 66 a will rotate in the A direction around therotational axis R2. More precisely, a rotational force is imparted bythe torsion coil spring 68 to the rack 66 so that the rack body 66 awill move to the outside of the second holder 55. Accordingly, as shownin FIG. 17, in a state in which the drive unit 70 is not fixed to thesecond lens group unit 77, the rack body 66 a rotates around therotational axis R2 so as to face the outside of the second holder 55,and stops with respect to the second holder 55 and the third lens groupsupport frame 56 in a state of being in contact with the first support55 a. Consequently, in attaching the drive unit 70 to the second holder55, the lead screw 64 a can be easily mated with the rack body 66 a.This affords a smaller size and facilitates the work during assembly.

(5)

Since the drive unit 70, the rotational axis R2, and the guide pole 63 aare disposed aligned in the circumferential direction, the drive unit 70and the rack 66 can be efficiently disposed on the outer peripheral sideof the third lens group G3, and the first profile line 70L can be madeto be closer to circular.

Also, the lead screw 64 a and the guide pole 63 a are disposed alignedin the circumferential direction, and the rotational axis R1 and thecenter R3 are disposed on substantially the same circumference.Accordingly, the drive unit 70 and the guide pole 63 a can beefficiently disposed on the outer peripheral side of the third lensgroup G3, while the lead screw 64 a can be disposed close to the guidepole 63 a. In other words, the interchangeable lens unit 2 can be mademore compact, while good drive force transmission efficiency can beensured.

(6)

Since the torsion coil spring 68 presses the rack 66 in the Z axisdirection against the first rack support 56 c, this suppresses movementof the rack 66 in the Z axis direction with respect to the third lensgroup support frame 56, and improves the positional accuracy of thefocus lens unit 75 with respect to the second lens group unit 77. Inother words, the accuracy of focal adjustment can be improved with thetorsion coil spring 68.

In particular, the torsion coil spring 68, which imparts rotationalforce in the A direction to the rack 66, also improves the positionalaccuracy of the rack 66 with respect to the third lens group supportframe 56. Accordingly, the single torsion coil spring 68 has the effectof both facilitating work during assembly and improving the accuracy offocal adjustment.

(7)

The first profile line 70L formed by the second lens group unit 77 andthe drive unit 70 substantially follows the inner peripheral face 50L ofthe fixed frame 50 when viewed in the optical axis direction, so thelayout of the members is more efficient and the interchangeable lensunit 2 can be more compact.

(8)

Since the terminals 64 f of the drive unit 70 stick out substantiallytoward the circumferential direction, the terminals 64 f are preventedfrom sticking out from the second profile line 77L of the second lensgroup unit 77. Consequently, the first profile line 70L formed by thesecond lens group unit 77 and the drive unit 70 can be made even closerto circular.

(9)

As shown in FIGS. 9 and 10, since the second lens group unit 77, thefocus lens unit 75, and the drive unit 70 consist of a single assembly,confirmation of the operation of the focus lens unit 75, measurement ofdrive accuracy, and so forth can be carried out before theinterchangeable lens unit 2 is in a completed state. Consequently, theprobability that drive error will occur in the focus lens unit 75 in thecompleted interchangeable lens unit 2 can be kept low, and themanufacturing efficiency can be increased for the interchangeable lensunit 2 and the digital camera 1.

(10)

Since the constitution described above allows the interchangeable lensunit 2 to be made more compact, the overall digital camera 1 can also bemore compact.

Other Embodiments

Embodiments of the present invention are not limited to those givenabove, and various modifications and alterations are possible withoutdeparting from the gist of the present invention. Also, the embodimentgiven above is essentially a preferred example, and is not intended tolimit the present invention, its applications, or its scope ofapplication.

(1)

In the above embodiment, the digital camera was capable of capturingboth still and moving pictures, but may instead be capable of capturingonly still pictures, or only moving pictures.

(2)

The above-mentioned digital camera 1 may be, for example, a digitalstill camera, a digital video camera, a mobile telephone equipped with acamera, or a PDA equipped with a camera.

(3)

The above-mentioned digital camera 1 do not have a quick return mirror,but may have a quick return mirror as do conventional single reflex lenscameras.

(4)

The configuration of the optical system L is not limited to that in theembodiments. For example, the third lens group G3 may consist of aplurality of lenses, and the second lens group G2 may consist of asingle lens.

(5)

In the above embodiment, the exposure time to the imaging sensor 11 wascontrolled by operating the shutter unit 33, but the exposure time ofthe imaging sensor 11 may instead be controlled by an electronicshutter.

(6)

In the above embodiment, electronic tracking was performed by the lensmicrocomputer 40, but a command may be sent from the body microcomputer10 to the lens microcomputer 40, and the control of the electronictracking may be performed on the basis of this command.

(7)

In the above embodiment, the first profile line 70L formed by the secondlens group unit 77 and the drive unit 70 was substantially circular. Thephrase “the first profile line 70L is substantially circular” hereencompasses not only a case in which the first profile line 70L iscompletely circular, but also a case in which the first profile line 70Ldeviates from being circular to the extent that the interchangeable lensunit 2 size can still be reduced.

In determining whether or not the first profile line 70L issubstantially circular, even if a portion is provided that sticks out tothe outside, such as a cam pin, the shape of that portion is not takeninto account. For instance, we do not take into account the shape of aportion that sticks out to the outside when viewed in a direction alongthe optical axis AZ and comes into contact with other members, such asthe cam pin 82 or the protrusion 55 b.

(8)

The angle at which the drive unit 70 is attached with respect to thesecond holder 55 is not limited to the attachment angle shown in FIG.16, as long as the motor holder 64 c faces toward the third lens groupG3. For example, as shown in FIG. 18, as long as it is disposed within arange of from the imaginary line N1 to the imaginary line N2 when viewedin the Z axis direction (within a range of an attachment angle θ), theimaginary line N will overlap the third lens group G3, so the firstprofile line 70L can be kept substantially circular.

The invention claimed is:
 1. A lens barrel, comprising: a first lensunit including a first lens element and a first lens support framesupporting the first lens element; a second lens unit including a secondlens element and a second lens support frame supporting the second lenselement, and being supported by the first lens unit to be movable in anoptical axis direction of the first lens element with respect to thefirst lens unit; and a drive unit arranged to be used to drive thesecond lens unit with respect to the first lens unit, and fixed to thefirst lens unit, the drive unit including a support plate fixed to thefirst lens unit to face the second lens element and an actuator with adrive shaft arranged to be rotatable around a first rotational axis,wherein, when viewed in the optical axis direction, the drive unit isfixed to the first lens unit so that a first profile line formed by thefirst lens unit and the drive unit is substantially circular, the secondlens unit includes a transmission member supported rotatably around asecond rotational axis by the second lens support frame and arranged toconvert the rotary motion of the drive shaft into linear motion in theoptical axis direction, and an elastic member arranged to impartrotational force around the second rotational axis to the transmissionmember so that the transmission member moves to the outer peripheralside with respect to the second lens support frame, the transmissionmember includes a transmission member body having an approximate U shapethat opens on the opposite side from the second rotational axis, andarranged to transmit drive force from the drive unit, and thetransmission member body opens toward the approximate circumferentialdirection in a state in which the drive unit is fixed to the first lensunit.
 2. An imaging device, comprising: a lens barrel including a firstlens unit including a first lens element and a first lens support framesupporting the first lens element, a second lens unit including a secondlens element and a second lens support frame supporting the second lenselement, and being supported by the first lens unit to be movable in anoptical axis direction of the first lens element with respect to thefirst lens unit, and a drive unit arranged to be used to drive thesecond lens unit with respect to the first lens unit, and fixed to thefirst lens unit, the drive unit including a support plate fixed to thefirst lens unit to face the second lens element and an actuator with adrive shaft arranged to be rotatable around a first rotational axis; anda camera body supporting the lens barrel, wherein, when viewed in theoptical axis direction, the drive unit is fixed to the first lens unitso that a first profile line formed by the first lens unit and the driveunit is substantially circular, the second lens unit includes atransmission member supported rotatably around a second rotational axisby the second lens support frame and arranged to convert the rotarymotion of the drive shaft into linear motion in the optical axisdirection, and an elastic member arranged to impart rotational forcearound the second rotational axis to the transmission member so that thetransmission member moves to the outer peripheral side with respect tothe second lens support frame, the transmission member includes atransmission member body having an approximate U shape that opens on theopposite side from the second rotational axis, and arranged to transmitdrive force from the drive unit, and the transmission member body openstoward the approximate circumferential direction in a state in which thedrive unit is fixed to the first lens unit.
 3. A digital camera,comprising: a lens barrel including a first lens unit including a firstlens element and a first lens support frame supporting the first lenselement, a second lens unit including a second lens element and a secondlens support frame supporting the second lens element, and beingsupported by the first lens unit to be movable in an optical axisdirection of the first lens element with respect to the first lens unit,and a drive unit arranged to be used to drive the second lens unit withrespect to the first lens unit, and fixed to the first lens unit, thedrive unit including a support plate fixed to the first lens unit toface the second lens element and an actuator with a drive shaft arrangedto be rotatable around a first rotational axis; and a camera bodysupporting the lens barrel, wherein, when viewed in the optical axisdirection, the drive unit is fixed to the first lens unit so that afirst profile line formed by the first lens unit and the drive unit issubstantially circular, the second lens unit includes a transmissionmember supported rotatably around a second rotational axis by the secondlens support frame and arranged to convert the rotary motion of thedrive shaft into linear motion in the optical axis direction, and anelastic member arranged to impart rotational force around the secondrotational axis to the transmission member so that the transmissionmember moves to the outer peripheral side with respect to the secondlens support frame, the transmission member includes a transmissionmember body having an approximate U shape that opens on the oppositeside from the second rotational axis, and arranged to transmit driveforce from the drive unit, and the transmission member body opens towardthe approximate circumferential direction in a state in which the driveunit is fixed to the first lens unit.